Sensitizing photographic emulsion



June 15, 1937. W. ZEH 2,083,804

SENSITIZ ING PHOTOGRAPHIC EMULS ION Filed D60. '7, 1932- 700 J0 600 J0 500 J0 400 50 30 unsensijed sliver bromide emuson conzczmbg womL 4 per cem,L ofszfer od'de 700 '50 600 J0 500 5U 400 J0 300 Fig-4. .M

700 Jo 60o o .500 50 400 J0 0o ATTORNEY.

Patented June l5, 1937 SENSITIZING PHOTOGRAPHIC EMULSION Walter Zeh, Dessau in Anhalt, Germany, assignor to Agfa Ansco Corporation, Binghamton, N. Y., a corporation of New York Application December 7, 1932, Serial No. 646,215 In Germany December 15, 1931 14 Claims.

My present invention relates to sensitizing of photographic emulsions.

One of its objects is to provide such an emulsion the sensitivity of which is raised over the range of wave lengths to which the emulsion is normally sensitive. Another object is the dyes incorporated in the emulsions in order to increase their sensitivity. Further objects' will be seen from the detailed specification following hereafter.

It is known to sensitize silver-halide emulsions by incorporating in the same asymmetrically built trirnethinecyanines. Each of these dyes sensitizes the emulsion to which it is added for a definite spectral region which varies according to the ring systems forming the dye.

According to this invention I have found that asymmetrical trimethinecyanines containing two different nuclei linked together by a trimethenyl chain and which have been substituted in the a or a position (see the following general formula) constitute a class of important sensitizers. By incorporating these dyes corresponding with the following general formula Y and Z=S, Se, O, -CH=CH- or C(CH3)2 V and W=H, alkyl, alkoxy, amino groups, substituted amino groups, benzene or halide,

R and R=H. alkyl, subject to the condition that -CH=CH- or C(CH3)2.

R. and R' are not bothhydrogen r and r'=alky1 X =halide, perchlorate, para-toluenesulfonate, alkylosulfate, nitrate.

etc., or an alkoxy group, for instance, a. methoxy or ethoxy group, or halide, or benzene or an .amino-group, or a substituted amino group, for instance, alkylated or acylated amino groups.

r may be alkyl, for example, methyl, ethyl, propyl, 5 etc. X can be any suitable anion that will precipitate the dye, for instance, a halide, paratoluene sulfonate, alkylosulfate, perchlorate, nitrate or the like. 'Ihe benzene nuclei may contain one or more of the substituents enumerated. The trimethenyl chain may be substituted by one or two alkyl groups, for instance, methyl groups or ethyl groups but either the a or the a carbon atom being linked to an alkyl group. The dyes may have an asymmetrical character by linking, for instance, -a thiazole to a sele'nazole, etc., nucleus by 9, trimethenyl chain or the asymmetrical structure may be due to two differently substituted nuclei of the same base.

In the accompanying drawing there are shown some spectrograms of emulsions sensitized in accordance with the invention.

Fig. 1 shows the spectrogram of an unsensitized silver bromide emulsion containing about 4 per cent of silver iodide,

Fig. 2 shows the spectrogram of the same emulsion sensitized with [3-ethyl-benzthiazole- (2) ll-ethyl-benzselenazole- (2) l-a-'y-dimethyltrimethinecyanine iodide,

Fig. 3 shows the spectrogram of the same emul- 30 n sion sensitized with ra-ethyi-benzthiazoie-(z)1- 3 ethyl 5 diethylaminobenzthiazole-(2) l-umethyl-trimethinecyanine perchlorate, and

Fig. l shows the spectrogram of thesame emulsion sensitized with [3-ethyl-benzthiazole-(2)l- 35 [3ethyl-naphtho-2'.1':4-5th1azole(2) l-a-e'thyl` trimethinecyanine iodide.

The dyes are obtainable according to the desired solubility in form of the bromide, iodide, perchlorate, etc., and are used in a quantity as 40 usual for the known sensitizing dyes. 'I'his quantity amounts to about 5 to 20 milligrams per 1 kg. of emulsion ready for being cast which lcontains about 9 per cent of gelatin, 4.5 per cent of silver-halide, the rest being water. However, I do not wish to limit my invention to the quantities just indicated. the most suitable amount will in each case be found by a few comparative experiments. The dyes may be added tothe emulsion in form of solutions. Suitable solvents are the alcohols, for instance, methyl or ethyl alcohol which may be used anhydrous or diluted with water. 'Ihe dyes are applied to the emulsion during any stage` of its production, however, they are preferably added to the nished emulsion before being cast.

The dyes may likewise be added by coating the emulsion with them or by bathing the ilnished photographic material in a bath in which the dye is dissolved. Such a treatment may be as followsz-The photographic material to be sensitized is bathed in a solution containing 1 milligram of [3-ethyl-benzthiazole-(2)l-[3-ethy1- benzselenazole-(Z) lany dimethyl trimethine cyanine iodide in 50 to 100 cc. of an aqueous solution of methanol of 50 per cent strength for about 5 minutes. The material is then dried, whereupon it is ready for use.

The dyes are suited for sensitizing an emulsion made according to the boiling process as well as for sensitizing an emulsion made according to the ammonia process.

The production of the bases and of the dyes from the bases is analogous to known methods. The production of substituted selenazole bases has been described in the copending application Serial Number 637,131 led October 10, 1932 by Walter Zeh and the production of bases substituted by an amino group or a substituted amino group has been described in the co-pending application Serial Number 590,940 led February 4, 1932 by Dieterle et al.

'Ihe following examples serve to illustrate my invention.

benzthiazole (2)] [3 ethyl benzselenazole (2) l-a.'y-dimethyl-trimethinecyanine-iodide corresponding to the formula a mixture of 5 grams of Z-ethylbenzthiazoleethyl-iodide and 3.5 grams of diphenylformamidine is heated with 15 cc. of acetic anhydride to about 150 C. for about 1 hour. After cooling a yellow crystalline mass separates which is washed with acetic anhydride and ether. The

intermediate product thus obtained corresponding probably with the formula Example 1.--For producing the dye [3-ethyl After cooling f taining about 4 per cent of silver-iodide the dye imparts to it a range of sensitivity from about 500ml to about 680m with a maximum at about 605/141..

Example 2.-The dye [3-ethy1-benzthiazole- (2)] [3 ethyl-benzoxazole (2)] a methyl trimethinecyanine-iodide corresponding with the formula is obtainable by boiling the intermediate product described in Example 1 in 5 cc. of pyridine with 2 grams of Z-methyl-benzoxazole ethiodide and precipitating the dye from the orange red solution by the addition of about 5 cc. of an aqueous solution of potassium iodide of about l0 per cent strength. The dye may be recrystallized from alcohol and is then obtainable in form of orange red crystals.

'Ihe alcoholic solution of the dye showsan absorption maximum at a wave length of about 525ML.

Incorporated in a silver-bromide emulsion containing about 4 per cent of silver-iodide the dye imparts to ita range of sensitivity from about 510ML to about 610ml with a maximum at about 565ML.

Example 3,-The dye [3-ethy1-benzthiazole- (2) l- [3-ethyl5-diethylamino-benzthiazole (2) la-methyltrimethenecyanine-perchlorate corresponding with the formula 7 s S /7\ /i CH; H H 1 I 5 4 /l-=bc2 s 4 -Nim), a 'v N l\c1o4y may be made by boiling the intermediate product described in Example 1 dissolved in 10 cc. of pyridine with 3 grams of 2-methyl-5-diethylamino ethiodide. From the blue solution which forms, the dye separates in blue flakes after the addition oi' about 10 cc. of an aqueous solution of sodium perchlorate of 5 per cent strength.

The alcoholic solution of the dye shows an absorption maximum at a wave length of about 600ml..

Incorporated in a silver-bromide emulsion containing about 4 per cent of silver-iodide the dye imparts to it a range of sensitivity from about 510ML to about 700ml with a maximum at about 630M/J..

Example 4.-'-For producing the dye [3-ethylbenzthiazole (2)] [3 methyl naphtho 1'.2 :4.5-thiazole- (2) l a methyl trimethine cyanine-iodide corresponding with the formula a mixture of the intermediate product made according to Example l, 3 grams of 2methyl4-5 a-methyl-trimethinecyanine-iodide corresponding with the formula 6 7 se s/76\N c,m l i 1 CH: H H l1 5 2 2 t 4 riet-takt ,H5 02H5 is produced as follows. 5 grams of 2-ethylbenzselenazole ethiodide in 30 cc. of acetic anhydride are heated with 3.5 grams of diphenylformamidine for about 1 hour to P10-150 C. After cooling the product which has separated is removed by filtration and washed with acetic anhydride and ether. 'I'hls product is condensed with 2 grams of 2-methy1-6-diethylamino-benzthiazole ethiodide by heating the mixture in 10 cc. of pyridine. The dye precipitates from the blue solution in pyridine after cooling in form of blackish green crystal powder.

The alcoholic solution of the dye shows an absorption maximum at a wave length of about 605ML.

Incorporated in a silver-bromide emulsion containing about 4 per cent of silver-iodide the dye imparts to it a range of sensitivity from about 515ML to about 720ml with a maximum at about 630M.

Example 6.-When condensing the intermediate product described in Example 5 with 2 grams of 1.2.3.3.6-pentamethylindole-iodide instead of the 2-methyl-6-diethylamino-benzthiy azole-ethiodide and adding to the solution in pyridine a few cc. of an aqueous vsolution of sodium perchlorate the vdye [3-ethyl-benzselenmethyl trimethinecyanine perchlorate corresponding with the formula 3 l 0104 on.'

is obtained in form of a brown red crystal powder.

The alcoholic solution of the dye shows an absorptionmaximum at a wave length of about 555ML.

Incorporated in a silver-bromide emulsion containing about 4 per cent of silver-iodide the dye imparts to it a range of sensitivity from about 505W to about 650W with a maximum at about 600m.

Example 7.-The dye [3-ethyl-5-ethoxy-benzselenazole (2) li3-ethyl-5.6dimethoxybenzthi azole (2) l-a-methyl trimethinecyanineiodide corresponding with tbe formula CIB; I 03H5 ether it is condensed with 1 gram of 5.6-dimethoxybenzthiazole ethiodide in 5 cc. of pyridine, by boiling these ingredients for about 5 minutes. After the addition of water and cooling the dye precipitates in form of bluish black fiakes.

The alcoholic solution of the dye shows an absorption maximum at a wave length of about 595/142.

Incorporated in a silver-bromide emulsion containing about 4 per cent of silver-iodide the dye imparts to it a range of sensitivity from about 520ML to about 700ML with a maximum at about 630ml..

Example 8.--For producing the dye [3-ethylbenzthiazole-(2) ][3 ethyl-napli'tho 2.1' :4.5 thiazole (2) l-a-ethyl-trimethinecyanine iodide corresponding with the formula there is first made an intermediate product by heating 3 grams of 2-n.propylbenzthiazole ethiodide with 2 grams of diphenylformamidine in 10 cc. of acetic anhydride for about 1 hour to 140 C. To the reddish yellow mixture there is added ether which is decanted after the separation of the intermediate product. The latter is then washed with ether and hereafter condensed with 1 gram of 2methyl-6.7benzobenz thiazole ethiodide by boiling these compounds in 5 cc. of pyridine -for a short period of time. On the addition of about 5 cc. of water the dye is precipitated in form of bluish black flakes.

'I'he alcoholic solution of the dye shows an absorption maximum at a wave length of about 585W.-

Incorporated in a silver-bromide emulsion containing about 4 per cent of silver-iodide the dye imparts to it a range of sensitivity from about 510ML to about 660ML with a maximum at about 610ml..

It is to be understood that my invention is not limited to the foregoing examples or to the specic details given therein. Numerous other embodiments are possible and I contemplate as included within my invention all such modifications and equivalents as fall within the scope ofthe appended claims. So, for instance, the benzene nuclei may contain one or more substituents. 'I'he nomenclature used is familiar to every chemist skilled in the art and has the advantage oi' clearness. Numbering ofthe bases etc. is begun from the sulfur etc. of the 5 ring. vnumbering of the quinoline nuclei and of the dyes is begun from the nitrogen atom. The formulae of the dyes as given herein 'represent the molecular structure of my newfdyes as far as known. II, however, in future it should become evident that the formulae do not exactly correspond to the dyes, this fact will not affect my invention since the dyes will be easily identied by the method of producing the same which has been fully described in the examples and is analogous to known methods.

What I claim is:

l. A photographic material comprising a silve halide emulsion sensitized with an asymmetrical trimethinecyanine containing in its molecule an alkyl group linked to at least one of the lateral carbon atoms of the trimethenyl chain.

2. A photographic material comprising a silver halide emulsion sensitized with [B-ethyl-benzthiazole-(Z) l-[3-ethyl-benzselenazole-(2) l xy-dimethyl-trimethinecyanine iodide corresponding probably to the formula 7 S Se- 7 1 011.11 CH; 1 6 54 32 za 4t a B 'y N q I (IJzHs CzHs 3. A photographie material comprising a silver halide emulsion sensitized with [B-ethyl-benzthiazole- (2) l- [3-methyl-5 -fdiethylamino -benzthiaf le-(2) la-methyl-trimethinecyanine perchlorate corresponding probably to the formula 67 s s- 1 oHlH H1 4. A photographic material comprising a silver halide emulsion sensitized with [3-ethyl-benzthiazole- (2) l[3-ethy1naphtho-2'.1 :4.5-thiazo1e- (2) la-ethyl-trimethinecyanine iodide corresponding probably to the formula and having a range o! sensitivity from about 500ml to about 680ml with a maximum at about 605ml.

6.` A photographic material comprising a gelatino-silver bromide emulsion containing about 4% of silver iodide sensitized with [3-ethylbenzthiazole- (2) [3-ethy1-5-diethy1amino-benzthiazole- (2.) la-methyl-trimethinecyanine perchlorate corresponding probably to the formula and having a range of sensitivity from about 510ml to about 700ml with a maximum at about 680ML.

'7. A photographic material comprising a gelatino-silver bromide emulsion containing about 4% of silver iodide sensitized with [S-ethyI-benzthiazole-(2) l- [3 ethylnaphtho- 1'.2' :4.5 -thlazole- (2) ]-a-ethyl-trimethinecyanine-iodide corresponding probably to the formula and having a range of sensitivity from about 510ml to about G60/rp. with a maximum at about 610ML.

8. A photographic material comprising a silver halide emulsion sensitized with an asymmetrical 3-alkyl-trimethinecyanine salt containing in its molecule an alkyl group linked to at least one oi' the lateral carbon atoms of the trimethenyl chain.

9. A photographic material comprising a silver halide emulsion sensitized with a dye selected from the groupconsisting of 3-alkyl-trimethinecyanine iodides and perchlorates containing in its molecule an alkyl group linked to at least one of the lateral carbon atoms of the trimethenyl chain.

10. A photographic material comprising a silver halide emulsion sensitized with an asymmetrical 3-alkyl-trimethinecyanine salt containing in its molecule an ethyl group linked to at least one of the lateral carbon atoms of the trimethenyl chain.

l1. A photographic material comprising a silver halide emulsion sensitized with an asymmetrical 3-a1kyl-trimethinecyanine salt containing in its molecule a methyl group linked to at least one of the lateral carbon atoms of the trimethenyl chain.

12. A photographic material comprising a silver halide emulsion sensitized with an asymmetrical 3-alkyl-trimethinecyanine salt containing in its molecule a methyl group linked to both lateral carbon atoms o! the trimethenyl chain.

13. A photographic material comprising a silver halide emulsion sensitized with an asymmetrical carbocyanine salt selected from the group consisting of thiazole-,trimethine'cyanine salts, selenazole-trimethinecyanine salts and oxocarbocyanine salts containing in its molecule an alkyl group linked to at least one of the lateral carbon atoms of the trimethenyl chain.

14. A photographic material comprising a silver halide emulsion sensitized with an asymmetrical indole-trimethinecyanine salt containing in its molecule an alkyl 'group linked to at least one of the lateral carbon atoms of the trimethenyll chain.

WALTER ZEH. 

